Improvements to the management of registry secrets

[hev]

Several commands are likely to repeated time and time again by users of knctl and could be flattened into a single (or possibly two commands). Specifically the commands I expect to use over and over again are:

Current State

Create Docker Hub secret for pushing images

$ knctl basic-auth-secret create -s docker-reg1 --docker-hub -u <your-username> -p <your-password>

If necessary, create Docker Hub secret for pulling images

$ knctl basic-auth-secret create -s docker-reg2 --docker-hub -u <your-username> -p <your-password> --for-pulling

Create service account that references above credentials

$ knctl service-account create -a serv-acct1 -s git1 -s docker-reg1 [-s docker-reg2]

Proposed Improvement

A potential alternative could be something like.

$ knctl save-registry-secrets <your-username> <your-password> --docker-hub

This would store creds locally and once you have a knative cluster targeted run the following singe command (limit one set of credentials per registry for now)

$knctl configure-build-registry --docker-hub

Creates all the necessary secrets in Knative to execute the build commands. You could also automatically configure the build registry when you use knctl to deploy knative.